In crude oil exploitation technology, especially in the experimental oil exploitation technology, a large amount of overheated steam is injected into the underground, making the temperature of produced oil liquid of an oil well very high (usually 210° C.-270° C.). Therefore, the device used for crude oil exploitation must meet the conditions of high temperature and high pressure. A Chinese Patent with an application number 201320031213.1 provides a multi-way valve for use in such a high temperature and high pressure environment for oil exploitation, in which the rotary valve core of the multi-way valve is provided passing through the mounting holes of an upper valve body and a lower valve body and mounted on the upper and lower valve bodies by means of rolling bearings. At high temperatures, the rotary valve core will expand so that the diameter and length of the rotary valve core are greatly increased, especially that the length of the rotary valve core is increased more obviously. The rolling bearing can be installed at a certain axial clearance to compensate for the increase in the length of the rotary valve core, but this compensation is limited, and it only adapts to the situation of the rotary valve core with a small amount of elongation. When the rotary valve core has a relatively large amount of elongation in high temperature environment, the axial clearance of rolling bearings cannot compensate such that the rotary valve core abuts against the rolling bearing, thus the rotation of the rotary valve core is not smooth or even stuck (jammed). In addition, in high temperature and high pressure environment, oil leak phenomenon is prone to occur in a multi-way valve. In order to solve the above problems, the following points need to be considered:
1. Set a reasonable axial clearance of a rotary valve core so as to prevent the rotary valve core from being stuck when rotating due to the above reasons.
2. Use safe and reliable seal to prevent oil leak.
3. The rotary valve core is radial positioned so as to prevent the rotary valve core from adhering to the upper and lower valve bodies or being stuck caused by inconsistent expansion due to the difference between the internal and external temperatures.